code: def accept(self, path, ext, operator):
      if operator in ["resize", "save"]:
          return "OK"
      else:
          if ext in [
              ".bmp",
              ".dib",
              ".ppm",
              ".pbm",
              ".pgm",
              ".sr",
              ".ras",
          ]:
              return "Recommended"
          elif ext in [".jpg", ".jpeg", ".png", ".tif", ".tiff"]:
              return "OK"
          else:
              return "NG"
  
file_path: nnabla/python/src/nnabla/utils/image_utils/backend_events/cv2_backend.py
imports: from __future__ import absolute_import, division
  import cv2
  import numpy
  from nnabla.logger import logger
  from .common import upscale_pixel_intensity, check_type_and_cast_if_necessary, _imread_before, _imread_after, _imsave_before, _imresize_before, _imresize_after
  from .image_utils_backend import ImageUtilsBackend
label_desc: Use image node_id 7 for calling the Cv2Backend obj's underlying member method code with example usage: obj.accept(path, ext, operator) and returns: str, str, str, str